Question: Khan.scratchpad.disable(); Luis sells magazine subscriptions and earns $$4$ for every new subscriber he signs up. Luis also earns a $$30$ weekly bonus regardless of how many magazine subscriptions he sells. If Luis wants to earn at least $$81$ this week, what is the minimum number of subscriptions he needs to sell?
Solution: To solve this, let's set up an expression to show how much money Luis will make. Amount earned this week $=$ $ $ Subscriptions sold $\times$ Price per subscription $+$ Weekly bonus Since Luis wants to make at least $$81$ this week, we can turn this into an inequality. Amount earned this week $\geq $81$ Subscriptions sold $\times$ Price per subscription $+$ Weekly bonus $\geq $81$ We are solving for the number of subscriptions sold, so let subscriptions sold be represented by the variable $x$ We can now plug in: $x \cdot $4 + $30 \geq $81$ $ x \cdot $4 \geq $81 - $30 $ $ x \cdot $4 \geq $51 $ $x \geq \dfrac{51}{4} \approx 12.75$ Since Luis cannot sell parts of subscriptions, we round $12.75$ up to $13$ Luis must sell at least 13 subscriptions this week.